Alkylpolyglycolether sulfosuccinates and alkylarylpolyglycolether sulfosuccinates are anionic surfactants that play an important part as emulsifiers in the industrial production of polymer dispersions. Concentrated aqueous solutions of such anionic surfactants show a peculiarity in rheological behavior which entails serious practical problems. Aqueous surfactant solutions of high concentration, for example, those with an active substance content of 50 wt. % or more, have the consistency of a thick gel or a paste of low fluidity and are not pumpable. If attempts are made to dilute such gels with water, the viscosity does not decrease, as would be expected, but instead initially rises to unexpectedly high values.
Because of this rheological peculiarity, emulsifiers of the type mentioned are mostly commercially available in the form of dilute aqueous solutions. Solutions of high concentration can only be produced by the addition of up to 20 wt. % lower alcohols, such as ethanol or isopropanol. However, the presence of organic solvents, for example the alcohols mentioned, in polymer dispersions is not always desirable for end uses thereof. In addition, because they are readily flammable, they involve a considerable safety risk during the manufacture of the emulsifiers as well as during transport, storage and use. Also, even slight shifts in the water/alcohol ratio in such concentrates can lead to undesirable sedimentation problems in the concentrates.
The fact that the stage of a thick gel which is no longer pumpable is frequently passed through during the dilution of aqueous surfactant concentrates which contain no alcohol causes considerable problems industrially. For example, lumps of gel, once formed, can only be redissolved with great difficulty. The valves of feed devices can thus become clogged, and changes in concentration may occur during metering. Finally, for the reasons mentioned, the dilution of such aqueous surfactant concentrates is a very time-consuming process.